OBJECTIVES: This study aimed to perform a review of the most frequently used databases in the European Union electronic Register of Post-Authorization Studies (EU PAS Register®) and stratify those by geographical distribution and therapeutic area.

METHODS: This study reviewed the finalized observational studies registered in the EU PAS register® that are publicly available via the European Network of Centers for Pharmacoepidemiology and Pharmacovigilance (ENCePP) website. All studies registered from the registry's inception until the 20th of January 2023 were taken into consideration. Only PAS conducted in European countries with established databases were included. Studies conducted via prospective data collection, surveys, medical chart reviews and cohort studies, were excluded.

RESULTS: We have identified 1090 finalized observational studies registered in the EU PAS register® from the start of the register until 20 January 2023. Of those, 392 have been conducted using established European databases. United Kingdom remains the most utilized source of Real-World Data (RWD) for PAS, followed by Germany and France, while the Nordic countries (Sweden, Denmark, Finland, Norway) provide a significant source of RWD for PAS.

CONCLUSIONS: Only the imposed PAS have an obligation to be recorded in the EU PAS register®. However, the same does not apply for the non-imposed PAS, thus limiting the accurate determination of the databases used across all categories of PAS. Furthermore, the lack of study protocol and/or results alongside the occasional inaccurate information provided on the studies’ entries, obstructs the proper logging of databases and countries involved in PAS. If changes were made to make data entry more structured and clarified, the EU PAS register® would accomplish better transparency and contribute towards a better understanding of the RWD utilized for PAS.